Mozilla Firefox version 11.x+ has support for 3D view. It is a WebGL based website visualization tool that highlights page structure. You can see relationship between your code and the page output by stacking elements as they are nested in the DOM and lets you see elements that are hidden or off the page. You can zoom in and out, rotate and pan the view to see the page from any angle that is helpful to you. In this blog post I will explain how to enable 3D view on X11. Please note that the 3D view is not for your daily browsing needs. It is useful for finding out bugs such as nesting issues or even XSS vulnerabilities. Personally, I use 3D view as a tool to understand divs, spans, and other elements on the page.
Mozilla has released Firefox version 14. Early last month, Mozilla had released Firefox 13. Firefox 14 has new features that make browsing more secure and Web applications like games more powerful.